It is known in the art to provide the mobile, water conduit-supporting towers of irrigation systems with drive wheels that propel the towers over ground to be irrigated. Typically, such towers include at least a pair of wheel assemblies at the base of the tower, each assembly comprising a single drive wheel powered by an electric or hydraulic motor.
It would be desirable in some instances to increase the ground-engaging surface area or “foot print” of each wheel assembly, such as where the wheel assemblies are steerable. However, providing larger tires or attaching special enlarged traction structures to the existing wheels necessarily increases the load on their existing drive motors and gearboxes, which can cause the units to malfunction or fail prematurely.
The present invention achieves the desired increase in surface area through the provision of a separately driven second wheel for each wheel assembly. Both wheels of each assembly are driven in unison and at the same speed but by separate drive motors. Preferably, the two wheels share a common axis of rotation but have separate drive shafts that are driven by separate motors. In one preferred form of the invention, the two wheels are disposed in closely spaced apart, side-by-side relationship. Preferably, the wheels are supported on a yoke having an upright, rotatable spindle and a pair of upright, laterally spaced legs that depend from the spindle at its lower end. The drive motors and gearboxes for the two wheels are duplicates of one another and are electrically interconnected.